The present invention relates to methods and apparatus for generating, detecting, and/or controlling ultrasound signals and in particular to methods and apparatus for focusing ultrasound signals to provide therapy to tissue at a desired location.
The treatment of tissue with high intensity focused ultrasound (“HIFU”) energy is known in the art. As used herein the term “HIFU Therapy” is defined as the provision of high intensity focused ultrasound to a portion of tissue at or proximate to a focus of a transducer. It should be understood that the transducer may have multiple foci and that HIFU Therapy is not limited to a single focus transducer, a single transducer type, or a single ultrasound frequency. As used herein the term “HIFU Treatment” is defined as the collection of one or more HIFU Therapies. A HIFU treatment may be all of the HIFU Therapies administered to a patient, or it may be a subset of the HIFU Therapies administered. As used herein the term “HIFU System” is defined as a system that is at least capable of providing a HIFU Therapy.
The Sonablate® 500 system available from Focus Surgery located at 3940 Pendleton Way, Indianapolis, Ind. 46226 is a HIFU System designed to provide high intensity focused ultrasound therapy to tissue. The Sonablate® 500 system is particularly designed to provide HIFU Therapy to the prostate. However, as stated in U.S. Pat. No. 5,762,066, the disclosure of which are expressly incorporated by reference herein, the Sonablate® 500 system and/or its predecessors may be configured to treat additional types of tissue.
The Sonablate® 500 system generally includes a transducer configured to image the tissue and to subsequently provide a HIFU Treatment to the tissue. The transducer is translated and/or rotated to image various portions of the tissue and to provide HIFU Therapy to various portions of the tissue. The transducer is moved by mechanical methods, such as motors, under the control of a controller. A typical HIFU Treatment includes first imaging the tissue of interest by moving the transducer to image different regions of the tissue. Next, a treatment plan is developed to target various portions of the tissue for treatment. The transducer is then moved to an appropriate location to provide HIFU Therapy to a particular portion of the tissue and the particular portion of the tissue is treated with HIFU Therapy. The treated site is then imaged to determine the effects of the HIFU Therapy. The positioning of the transducer, provision of HIFU Therapy, and post-imaging steps are repeated for each particular portion of tissue which is to be treated.
A need exists for a HIFU System that can treat various portions of tissue at differing focal depths and/or longitudinal locations without the need to move the associated transducer and without the formation of unwanted concentrations of HIFU energy outside of the focal zone, including off-axis. Further, a need exists for a HIFU capable system that can image multiple portions of tissue without the need to move the associated transducer.
In an illustrated embodiment of the present invention, a method of treating tissue with a HIFU System including a transducer is provided. The method comprising the steps of: providing HIFU Therapy to a first portion of the tissue, the first portion being located at a first distance from the transducer; providing HIFU Therapy to a second portion of the tissue, the second portion being located at a second distance from the transducer; maintaining a generally constant f-number with the transducer when providing HIFU Therapy to both the first portion of the tissue and the second portion of the tissue.
In another illustrated embodiment of the present invention a method of conducting a HIFU treatment to a target tissue is provided. The method comprising the steps of: positioning a transducer proximate to target tissue, the transducer having a variable aperture; imaging the target tissue; selecting a plurality of treatment sites within the target tissue to be treated with HIFU Therapy, a first treatment site being located a first distance from the transducer and a second treatment site being located a second distance from the transducer; and providing HIFU Therapy to the plurality of treatment sites with the transducer, the transducer having a first aperture when providing therapy to the first treatment site and having a second aperture when providing therapy to the second treatment site, at least one of an active extent of the first aperture and an active extent of the second aperture being chosen so that a ratio of the second distance to the active extent of the second aperture is generally equal to a ratio of the first distance to the active extent of the first aperture.
In yet another illustrated embodiment of the present invention, a transducer for use with a HIFU System comprising: an active surface having a plurality of transducer elements; and a controller operably coupled to the transducer, the controller being configured to select which transducer elements emit acoustic energy and to control such emissions to focus the acoustic energy at various focal depths so that the active surface has a generally constant f-number at the various focal depths.
In a further illustrated embodiment of the present invention, a method for controlling the emission of acoustic energy from a plurality of transducer elements of a multi-element transducer such that the acoustic energy is focused at a desired location. The method comprising the steps of: determining a phase and an amplitude required for each transducer element; providing a reference continuous wave signal to each transducer element; digitally generating from the reference signal a delayed and pulse-width modulated signal for each transducer element; generating an amplitude modulated analog signal for each transducer element based on the delayed and pulse-width modulated signal for the respective transducer element; and driving the transducer element with the amplitude modulated analog signal.
In still a further illustrated embodiment of the present invention, a method of imaging a targeted tissue and treating portions of the tissue with HIFU Therapy is provided. The method comprising the steps of: providing a transducer having a longitudinal extent at least equal to a longitudinal extent of the targeted tissue, the transducer including a plurality of individually controlled transducer elements; electronically scanning a first sub-aperture of the transducer to generate at least one image of the targeted tissue while the transducer is held in place longitudinally; identifying portions of the targeted tissue for treatment with HIFU Therapy; treating each of the identified portions of the targeted tissue with HIFU Therapy.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.